The present invention relates to a process for the manufacture of a sheet, band, or strip of zirconium alloy or hafnium alloy which comprises hot roughing of an ingot into a blank, followed by hot rolling of this blank in the alpha domain, this hot rolling including several passes which follow one or more reheatings in a furnace at one or more temperatures, each of which improves the formability of the blank, then cold rolling which includes one or more cycles of "rolling pinch passing/heat treatment".
A process of this type is known from the Applicant's patent FR-B-2599049 corresponding to EP-B-0246986 and U.S. Pat. Nos. 4,775,428 and 4,881,992. This patent discloses the manufacture by rolling of a 0.43 mm strip of Zircaloy 4 from a hot rolled band with a thickness of 6 mm. In the cold rolling of this strip, there are five cold rolling sequences with intermediate annealings, and each sequence actually consists of several cold rolling passes. The choice to stop the hot rolling at 6 mm is dictated by quality considerations, but the obvious disadvantage is the long duration of the manufacturing process and its cost.
On the other hand, in a process known from FR-A-2303865 corresponding to GB-A-1537930, a sheet of zirconium alloy for use in a nuclear reactor, for example of Zircaloy 4 with a thickness of 4 mm, is reheated up to at least 900.degree. C. by means of high-frequency induction. The reheating of the sheet is superficial. The use of a lower frequency makes it possible to reheat the entire thickness of the sheet, but with substantial temperature gradients and deformations during the rapid cooling which follows this reheating. The only reheating temperature given as an example is 900.degree. C., which corresponds to the alpha+beta domain in the case of Zircaloy 2 or 4.
Applicants have attempted to find a more economical way to handle the hot rolling while preserving or even improving the quality of the products obtained.